The light source box that uses the LED as the light source (hereinafter, “LED light source box”) is used, for example, as a light source for a projector. However, as in the case of other projector light sources (discharge lamps such as a metal halide lamp and an extra high pressure mercury lamp), high luminance must be achieved for the LED light source box. The amount of the light that the LED emits depends on the amount of current that is input. Accordingly, increasing the amount of light that is mitted by increasing the amount of current that is input can meet the demand of high luminance.
However, since the LED is low in quantum efficiency, most of electric energy input to the LED is converted into heat. Accordingly, when the amount of current that is input is increased, the amount of light that is emitted increases to lower light emission efficiency. Further, there is a possibility of thermal destruction of the LED. Therefore, to achieve a high-luminance LED light source box, means for effectively cooling the LED is essential.
Thus, Patent Literature 1 describes a light source device that includes a system to cool the LED by liquid and a projector that includes the light source device. The light source device described in Patent Literature 1 includes a box body constituting a part of a flow path through which the liquid circulates, and a mounting board housed in the box body. A LED element mounted on the mounting board is cooled by liquid passing through the flow path formed in the box body.